The present invention is directed to a method and apparatus for inspecting toothed articles such as splines. The basic technique of the present invention involves a rapid succession of span measurements which can be used to determine the quality of a workpiece.
The most common prior art method for determining the quality of splines involves the use of "go and no-go" gauges. In this method a "go" gauge having an opening which corresponds to the maximum tolerable spline dimension is placed over the spline being examined. If the "go" gauge does not fit over the part being inspected, the spline is larger than the maximum allowable size. Similarly, if a "no-go" gauge with an opening corresponding to the minimum allowable part size fits over a part being examined, the part is too small. Obviously the use of such gauges is tedious and it requires extensive manual labor which is costly and inefficient. Another disadvantage is that wear of the gauges necessitates their replacement. This is costly since each guage must be made to very precise dimensions. Furthermore, the timing of the replacement is a subjective decision which leads to variability in the inspection process.
Applicant's invention greatly simplifies the inspection of splines. In the Applicant's invention, a spline is rotatably supported in a cradle (or between centers). A pair of checking discs of the same hand are mounted on a pivoting arm. The two discs are mounted to a common rotating shaft carried by the pivoting arm. One of the discs is axially fixed and the other slides along the shaft. The discs are keyed to the rotating shaft and rotate in unison. When the discs are brought into engagement with the workpiece, it rotates about its axis in the cradle. The discs engage generally parallel oppositely directed tooth profiles on the workpiece. The discs are threaded with one side of the thread being straight for engagement with the spline teeth. While rotating, relative movement of the sliding discs is monitored by a linear voltage differential transducer. A continuous record of the movement of the sliding disc provides a continuous measurement which includes a succession of span measurements which can be used to sort workpiece splines according to their derivation from designed dimensions.
The objects and advantages of the present invention will be apparent upon a reading of the following specification read in conjunction with the accompanying drawings.